Bitumen is produced by the non-destructive distillation of crude petroleum during the refining process, making the exact composition of asphalt dependent on the chemical complexity of the original crude petroleum. Asphalt is a blend of bitumen and mineral substances but, within the scope of this invention, bitumen also encompasses asphalt. While no two bitumen specimens have the same chemical makeup, its composition can be divided into four main designations through analytic methods: saturates, aromatics, resins, and asphaltenes (otherwise known as SARA's). Bitumen behavior is greatly influenced by the relative concentration and chemical features of these four phases, especially that of asphaltene, the most polar of the phases. The asphaltene molecular structure has been measured over the decades and the finding is that the structure contains known hydroxyl (—OH) and amine (—NH) pendant groups. It is believed that under the right reaction conditions, these groups could be made to react with either monomeric and/or polymeric polyisocyanate and/or a prepolymer consisting of one or more polyester, polyether, hydroxyl-terminated polybutadiene, polycarbonate, and/or any imaginable hydroxyl-functional (functionality 2 or more) and polyisocyanate (e.g., see the polyisocyanate and polyol listing that can be used in U.S. Pat. No. 8,419,872, which is incorporated herein by reference). The reaction would create a bitumen/polyisocyanate adduct that can further react with —OH functional polyols of any molecular weight and/or any blend of functionality to improve the aforementioned physical properties of the asphaltic membranes.